Mechanical servo brake



Oct. 14, 1941. 5 LA BR|E 2,258,897-

INVENTOR.

7:7 3 [006275119576 6 .36 By W M -6 52 ATTORNEY Oct. 14, 1941. E. LA BRIE MECHANICAL SERVO BRAKE Filed July 26, 1955 5 Sheets-Sheet 3 IN V EN TOR.

ATTORNEY Oct. 14,1941. 5 LA BRlE 2,258,897

MECHANICAL SERVO BRAKE Filed July 26, 1935 5 Sheets-Sheet 4 INVENTOR.

ATTORNEY Oct. 14, 1941. L. E. LA BRIE MECHANICAL SERVO BRAKE Filed July 26, 1935 5 Sheets-Sheet INVENTOR. 100651? E. ZflfiP/E A TTORNEY Patented Oct. l4,

UNITED STATES PATENT OFFICE 2.25am I I MncnANroAL snnvo 3m Ludger-E- La as... South Bend, ma, mimito Bendix Products Corporation, South Bend, Ind, a corporationof Indiana v, v

Application July 26, 1935, Serial No. 33,301 3 Claims. (01. 188-140) This invention relates to brakes for motor vehicles and more particularly to power means for operating vehiclebrakes, where the power is derived from some rotating part of a vehicle, preferably a drive member which is in constant drive relation with the vehicle wheels.

As is well understood in the art. the operation of vehicle brakes, requires considerable expenditure of energy upon the part of the operator, particularly where the vehicle is of the heavier type. The invention has to do with providing a. mechanism for employing the energy of the movingvehicle for applying the brakes, the mechanism including an operator controlled friction device adapted to take off a brake operating torqu from the propeller shaft of a vehicle or some other rotating part from which a brake operating torque may be obtained. More particularly the invention has to do with the employment of a drug type friction device for developing torque and linkage for suitably controlling the torque and applying the same to wheel brakes.

Accordingly an object of the invention is to provide an improved friction device including a control therefor for developing a brake operating torque and means for transmitting the torque to the vehicle brakes.

Another object of the invention is to provide a friction device for engagement with a rotating drum which device may transfer torque from the rotating drum to energize a brake linkage to any desired degree in accordance with the actuation of a control member.

A further object of the invention is to provide in a friction devic of the drum type for developing energy for actuating wheel brakes, a control therefor which will require a movement or energy which may always be substantially proportional to the energy to be applied to the wheel brakes by the friction device.

The above and other novel features of the invention will appear more fully hereinafter from the following detailed description when taken in conjunction with accompanying drawings. It is expressly understood, however, that the drawings are employed for purposesof illustration only and are not designed as a definition of the limits of the invention, reference being had for this purpose to the appended claims.

In the drawings wherein like reference numerals indicate like parts:

Fig. 1 illustrates a side elevation of a form of power take off of the lntemal expanding friction s ty Fig. 2 is a vertical section taken through Fig. 1;

Fig. 3 is an end elevation of the relatively stationary friction parts of Fig. 1. together with the rotary drum, the head of the drum being removed;

Fig. 4 is a section taken on line 4-4 of Fig. 3 showing the actuating cam therein and its mounting.

Fig. 5 is a top plan view of a portion of ,the torque developing element of Fig. 1 illustrating a method of transmitting developed torque to a brake linkage;

Fig. 6 is a modified form of the invention employing an external contracting friction band;

Fig. 7 is an end elevaticn of the modification of Fig. 6 with the brake drum flange removed;

Fig. 8 shows diagrammatically a further modification employing hydraulic control.

Fig. 9 is a vertical section of the torque developing portion of Fig. 8;

Fig. 10 is an end elevation of the modification of Figs. 8 and 9 with the brake drum head removed; and

Fig. 11 is a diagrammatic illustration of another form of linkage employed with the hydraulic control of Figs. 7-9 inclusive.

Referring to the drawings and particularly Figs. 1-5 inclusive, there is shown a rotatable friction dru'm 20, mounted for rotation with the propeller shaft of a vehicle, the drum in the embodiment shown being mounted on a flange plate 22 drivably connected to a shaft 24 emerging from the back side of a transmission gear box 26. The flange plate 22 may carry a universal joint housing 28 and drive a universal joint, not shown, housed therein, which latter is generally connected to a propeller shaft of the vehicle. It will readily be understood that the propeller shaft is preferably normally geared to certain wheels of the vehicle and must rotate with the wheels, thereby forming a reliable source of power for brake operation whenever the vehicle is moving.

Secured to the back side of the gear box 26 upon which is rotatably carried a backing plate or support and end closure 4|! for the drum, the backing plate 40 being retained on the bearing surface 28 by a shoulder 42, and a threaded collar ll.

The backing plate 40 is provided with a drum may be wrapped an operating cable It hereinafter more fully described. The backing plate.

also carries friction shoes 80 and I2 for engaging the internal surface of the drum 2|. The friction shoe 50 is shown as of T section and providedrwith a lining H, and anchored on a pin 86 secured to the backing plate. The friction shoe II, also of 'r section is provided with a relatively longer friction lining II and is adapted to anchor upon the pin I! through an adjustment ll comprising a clevis member 02 pivoted on said anchor, a screw member ll rotatably mounted in said clevis member '2 and including a notched or star wheel SI for adjustment and a threaded socket member ll notched to receive the notched end ll of the shoe 5!. A tension spring 12 connecting the shoes 50 and I2 and retaining shoe '2 in engagement with the adjustment also serves as a resilient detent to prevent rotation of the star wheel 86 except as desired.

To spread the friction shoes into engagement with the drum a lever and cam member I4 is provided, the same having a raised cam portion it arranged between the ends of the shoes II and 52. A stub 18 extending from the back side of the lever behind the cam is pivoted in a tangential slot 80 provided in a raised portion 8| of the backing plate. The outer end of the lever is provided with a hook I for receiving a flexible cable 82, having a flexible conduit 88 which may as shown in Fig. 5 extend through the backing plateat an angle. It will appear that the cable extends at right angles to the slot 8| in the backing plate, and that the flexible cable and conduit permit the necessary slight rotation of the backing plate during operation of the brake.

For adjustment, in addition to the link 60, an eccentric 80 is arranged in the backing plate adjacent the shoe ill and by means of the spring 92 and head 94 may be frlctionally held in any desired set position so that the eccentric cam may flx the release position of the shoe. One or more hold down springs 86 may be applied to the shoes to retain them slidably against the backing plate and a return spring II, adapted to urge the shoes to the release position" connects the two shoes and urges them into cam engagement.

Referring more'in detail to the actuating linkage for transmitting the torque developed by the friction device hereinabove described in Fig. 5, the cable 48 is shown as wrapped around the drum 4 and secured thereto as at I". The ends of the drum cable are in turn secured together and around a brake operating cable IN by means of suitable end flttings I02. The brake operating cable, as shown in Fig. 1, may extend to a short lever arm on the brake pedal I00 and to a long lever arm I" on a brake operating cross shaft Ill. The brake operating cable, adjacent the point of its attachment to the drum cable 48 may pass over a pair of spaced rounded guide members III and Ill, which will prefereably be greased to avoid friction.

In order thatthe pedal pressure and movement may be proportional to the degree of application of the vehicle brakes, the control cable 82 which actuates the internal expanding friction shoes, is according to this modification, after emer ing from the end ll of the flexible conduit, passed over a pulley Ill and thence to the lever I08. on the brake operating cross shaft Ill. The pulley, through a link I is attached to the brake pedal II in either of a series of holes I22, so that the effective lever length can be readily varied or adjusted. As will be well understood in the art the conduit end Ht of the conduit It will be flxed relative to the brake pedal by some suitable rigid support, which, however, of course, may be adjustable in position, as desired. Also it will appear that the lever ill on the cross shaft Ill may be of the pivoted type having a knee in so that the'bra-ke cross shaft may be operated by another source such as the well known hand or emergency lever, thereby overrunning the power operated linkage.

Operation of the power brake will readily be understood from the foregoing description. Movement of the brake pedal I" in a clockwise direction will tension the cable 82, actuating the cam I8 and frictionally expanding the friction shoes and 82 into engagement with the drum. Assuming the vehicle to be underway and the drum 2. to be rotating. a torque proportional to the pressure of shoe engagement will be produced which will tend to rotate the support plate II and its drum n on the support sleeve ll, thereby tensioning one end or the other of the drum cable ll and slackening the other end, depending of course on the directionof rotation of the drum 20 and the direction of movement of the motor vehicle.

The tensioning of the drum cable I acts to tension the brake operating cable I, thereby actuating the lever I and rotating the brake cross shaft Ill. The brake operating cable is also connected to the brake pedal I and a short lever arm 50 that some "feel may be transmlb ted to the brake pedal. 80 that the pedal travel may be proportional to the brake application, upon movement of the brake cross shaft lever Hit, the control cable" passes over a pulley Hi and thence to the brake cross shaft lever so that as fast as the vehicle brakes are applied the cable 82 is slackened so that it becomes necessary to further apply the brake pedal. It will, of course, be understood that the links may be suitably adjusted so that the degree of pedal travel may be arranged to suit individual oper ating tastes. Since many wheel brakes act differently when operated in one direction than in the other, it may be desirable to change the extent of the brake lining on the shoes II or I! so that the friction device may develop more or less torque in one direction than the other to compensate for the inequalities in the wheel brake or to give a warning in reverse braking of brake wear.

Referring to Figs. 6 and 7 illustrating a modifled form of the invention, there is shown a power take-off employing a friction device of the external contracting type. Referring more in detail, there will appear the usual transmission casing 22. on the rear of which is mounted a support sleeve 2" which carries a support bracket 23! which has a drum flange 224 carried on the support sleeve Ill. The shaft 2" extending from the transmission box is provided with a brake drum 138 which may, as shown, surround the usual universal Joint 2 coupling the shaft 2 with the usual propeller shaft, not shown. The brake drum III is surrounded by a band I" carrying a friction lining I which band is provided with a U-shaped guide and anchor engaging member 2 arranged about an axially extending anchor pin 2 carried on the support bracket 232. The screw Ill threaded in the anchor pin Ill is adapted to dJust the friction band relative to the rotating drum and take up for wear.

- The free ends of .the friction band 242 are provided with brackets 252 and 254 to which are attached a flexiblecable 253 and conduit Ill respectively. Th cable is adjustably'carried by the bracket 232 by reason of the nut 2ll and a spring 232 is arranged about the cable 253 between the brackets to release the friction ahoe from engagement with the drum. The conduit 253 is rigidly supported at 2" and the cable may extend therefrom about a pulley 233 actuated by the brake pedal. About the drum 234 on the anchor carrying bracket 232 is a flexible drum cable 234, the ends of which are provided with fittings 233 for engagement with a brake actuating cable I04 which may pass over guide member The operation of the modification shown inv Figs. 6 and 7 will be the same as that of the modification shown in Figs. 1 to since it will appear that tensioning of the cable 253 will cause the friction band 242 to engage the drum 233 which, if rotating, will transmit a vtorque to the anchor bracket 232 and the drum 234 thereby tensioning one end or the other of the cable 254.

In Figs. 8 through 11, a further modified form of invention with two variations is shown wherein the control of the friction device is accomplished hydraulically. Referring to Fig. 9, the transmission casing 326 is again illustrated as having a support collar 330 about which a backadapted to operate the master cylinder 3 which isconnected through a fiexible'conduit 4" to the brakecylinder 353. The pedal is also connected through acable' 4 l4 around apulley 4| l and back to a lever 4l2 oppositely directed from the brake peda1'4ll but rigid therewith. The drum cable 343 as best shown in Fig. 10. which is secured on the drum 340 en ages the cable 434 in the manner shown in Fig. 5 and tightens the cable 404 around guide member 4l4a' upon operation of the friction power take-oil. The wheel brakes maybe connected to the lever 4l2 or to the cross shaft 4 which rotates as a part thereof.

In Fig. 11 a modified form of hook-up is shown wherein the master cylinder is operated by seplever 420 about the cross shaft 4l3 that hydraulic fluid will be expelled from cylinder 403 which will, in turn, actuate the friction device in producing torque on drum 343 thereby tensioning the cable 404' and applying power to the cross shaft lever 420.

The operation of the structure of Figure 8 is the other endsof cable 343 and tightening the tension member 404. The pull on the tension member 404 exerts force at two points. One end .of the element 404 rotates the lever H2 in a clockwise direction. This efiects the turning of "cross shaft 4 to apply the road wheel brakes ing plate or support disc 340 is mounted. The v v backing plate is also provided with a drum and 352 respectively. Return springs 312 and 314 are provided for the shoes in order to maintain them normally in non-engaged position.

In order to fix the release position of the brake I shoes a novel adjustment is provided for each shoe adjacent the free end thereof and carried in a backing plate. The adjustment consists of a threaded pin 330 having a conical end 332 adapted to engage an edge of the shoe 350, the pin having an exposed end 334 conveniently shaped to fit a spanner. The backing plate is provided with a threaded hole 333 to receive the pin and is also provided with an axially extending groove 333 into which a spring pressed ball 330 may seat thus tending to lock the adjustment against undesired movement. It will, of course, be understood that the groove 333 is only of sumcient depth to act as a detent but of insufficient depth to prevent the ball from being thrust inwardly whenever the pin is turned by a spanner.

' As shown in Fig. 8, the brake lever 403 is through suitable mechanical linkage. Since the levers H2 and 403 are rigidly connected, this motion of lever 2 moves lever 405 to apply further pressureto the fluid in master cylinder 403. The other end of the tension member 404 is attached to lever 403 and tends to rotate that lever in a counterclockwise direction, thus opposing the brake-applying rotation of the cross shaft 4. This opposing force exerted on lever 406 is proportional to the force exerted by the servo mechanism, and is therefore proportional also to the force applied to lever 2 to actuate the wheel brakes. -Since the opposing, or reaction force, works on a comparatively small leverage, the reaction or feel on the operator's foot is a small percentage of the brake-applying force. Since the forces acting around the shaft 4" will tend to reverse the direction of rotation of the cross shaft unless the operator continues to move the pedal lever 405 in a clockwise direction, the distance of pedal travel will be proportionate to the degree of brake application.

The operation of the modification of Figure 11 is much the same.- Clockwise rotation of the pedal lever 424 by the operator will swing the lever 420 in a counterclockwise direction about the shaft 3. Rotation of the shaft 8 begins the application of the wheel brakes. At the same time, fluid is displaced from the master cylinder 403, through the conduit 0, into the hydraulic motor spreading the shoes of the servo brake mechanism into contact with the drum. Rotation of the drum turns the plate 343, tensioning the cable 343 andtightening the tension member 404'. Thus a brake-applying force is applied to the lever 420 and a reaction force is applied to the pedal lever 424, tending to oppose movement thereof, unless the operator exerts greater force thereon and moves the pedal lever a further distance in a clockwise direction to further apply the brakes. I

It will thusbeseen that a power brake is provided wherein the. brake pedal moves in proportion to theactuation of the vehicle brakes'and wherein the pedal pressure is likewise-proper tioned to the brake actuation, the power source for brake operationbeing derived from rotation of some part of the vehicle transmission'separate from the wheels themselves. It will be readily appreciated that such an arrangement affords unlimitedpower so that brakes of a simple form may be employed whose characteristics are well known and easily controlled.

Although several modifications of the invention have been illustrated and described it should be understood that the invention is not limited thereto but may be embodied in other mechanical arrangements and forms. For example, the various features of any one of the modifications might be substituted for those of the other modincations. As such and other changes in construction and arrangement may be made without departing from the spirit of the invention as will be apparent to those skilled in the art, reference will be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

1. In a mechanical servo power brake, a friction drum rotatable by the wheels of a vehicle, friction means radially movable for engaging said drum, a support for said friction means rotatable in either direction, means to apply said friction means to the drum, a vehicle brake linkage actuated in one direction by rotation of said support means in either direction, and a reaction connection between said applying means and said vehicle brake linkage.

member, means for transmitting the torque derived from the friction device to apply a brake remote. therefrom. hydraulic means for engaging saidfriction' device with the rotatable member in varying degree,and means for operating thehydraulicengagingmeans andhaving amechanicalreaction connection withthe transmitting means separate from said hydraulic means whereby the brake applying movement of the op-' erating means may be proportional to the developed force of the transmitting means.

5. In an automotive vehicle servo power brake,

a wheel brake operating cross shaft, a lever 2. In a power brake, a power driven rotatable member, a friction device for engaging said member, means for transmitting the torque derived from the friction device to apply a brake independent thereof, hydraulic means for engaging said friction device with the rotatable member, an operator operated member for applying pressure to said hydraulic means, and means comprising a mechanical reaction connection between the torque transmitting means and the operator operated member separate from said hydraulic means whereby the developed force of the transmitting means may be proportional to that of said hydraulic means.

3. In a power brake, a power driven rotatable member, a friction device for engaging said member, means for transmitting the torque derived from the friction device to apply a brake remote therefrom, hydraulic means for engaging said friction device with the rotatable member in varying degree, and means for operating the hydraulic engaging means and having a reaction connection with the transmitting means whereby the brake applying movement of the operating means may be proportional to the brake applying movement of the transmitting means.

4. In a power brake, a power driven rotatable member, a friction device for engaging said thereon, a brake pedal, an operating cable having a short lever connection on the brake pedal and a connection to the cross shaft lever, a power driven rotatable drum member, a friction device adapted to enga e said power member, means for transforming the torque derived by said friction device into tension in said operating cable. and control means for engaging said friction device with the rotatable drum member.

6. In an automotive vehicle servo power brake, a wheel brake operating cross shaft, a lever thereon, a brake pedal, an operating cable having a short lever connection on the brake pedal and a connection to the cross shaft lever, a power driven rotatable drum member, a friction device adapted to engage said power member, means for transforming the torque derived by said friction device into tension in said operating cable, and control means for engaging said friction device with the rotatable drum member, said control means having a reaction connection to the cross shaft lever.

7. In a servo power brake a friction drum rotatable by the wheels of a vehicle, friction means radially movable for engagement with said drum, engaging means, a support plate for carrying said friction means and the torque derived thereby from the drum, said support plate being mounted for rotation about the axis of said drum, a cable drum carried by said support plate. tension cables leaving said cable drum tangentially and converging at a point of connection with a common wheel brake operating linkage, said tension cablesbeing secured to said cable drum to wrap and unwrap therewith, an operator operated member for applying pressure to torque in either direction into tension to operate abrake, means for engaging the friction device with the power driven member, and an operator operated member for applying force to the engaging means having a reaction connection independent of the engaging means with the torque transforming means.

LUDGER E. LA BRIE. 

